1. Field of the Invention
Example embodiments of the present invention relate to a focusing apparatus and a lithography system using the same, and more particularly, to a focusing apparatus and a lithography system using the same, which can adjust a uniformity of an electromagnetic field.
2. Description of the Related Art
Various lithography techniques may be used for patterning a surface of a substrate into a desired pattern in a semiconductor manufacturing process. An optical lithography technique may be used for surface patterning. However, optical lithography techniques may have a limitation with regard to a possible linewidth. Accordingly, a next generation lithography (NGL) technique capable of realizing a finer semiconductor integrated circuit (IC) having a nano-dimensional linewidth has been proposed. Examples of NGLs include electron-beam lithography (EBL), ion-beam lithography (IBL), extreme-ultraviolet lithography (EUL), and proximity X-ray lithography (PXL).
An EBL system is a type of system for patterning an electron resist coated on a substrate into a desired pattern using an electron beam. In a conventional EBL system, an electron beam can be emitted only on a very-limited area, and thus an emitter emits an electron beam toward an electron resist while moving along a pattern to be formed on the electron resist. Accordingly, a conventional EBL system may undesirably require a lot of time to complete one pattern.
A structure of a conventional electron-beam lithography system capable of emitting a large-area electron beam is schematically illustrated in FIG. 1.
Referring to FIG. 1, a conventional electron-beam lithography system may include a vacuum chamber 10 surrounding a space for processing a wafer 30. The interior of the vacuum chamber 10 may maintain a desired vacuum state via a vacuum pump 12. The vacuum pump 12 may be made of nonmagnetic material, for example, plastic, aluminum, aluminum alloy, stainless steel, or copper so as to reduce or prevent a magnetic flux from leaking therefrom.
An electron-beam emitter 20 for emitting an electron beam may be arranged in the vacuum chamber 10, and the wafer 30 may be arranged to face the electron-beam emitter 20 while being spaced apart therefrom by a desired interval. The electron-beam emitter 20 may have thereon a patterned mask 22 of a desired pattern, and thus an electron beam emitted from the emitter 20 may be emitted through a portion not covered with the patterned mask 22. The emitted electrons may pattern an electron resist 32 on the wafer 30 into a pattern identical to the pattern of the mask 22.
The wafer 30 may be supported by a wafer holder 42 in the vacuum chamber 10, and the electron-beam emitter 20 may be supported by an emitter holder 41 in the vacuum chamber 10.
An upper magnet 61 may be arranged proximate to an upper portion of the vacuum chamber 10 in such a way to be spaced apart from a top wall of the vacuum chamber 10 by a desired interval, and a lower magnet 62 may be arranged proximate to a lower portion of the vacuum chamber 10 in such a way to be spaced apart from a bottom wall of the vacuum chamber 10 by a desired interval. The upper and lower magnets 61 and 62 may provide a magnetic field in the vacuum chamber 10. The upper magnet 61 may include a ferromagnetic core 61a and a coil 61b wound around the periphery of the core 61a, and the lower magnet 62 may include a ferromagnetic core 62a and a coil 62b wound around the periphery of the core 62a. 
An upper pole piece 71 may be arranged to penetrate the top wall of the vacuum chamber 10, and magnetically come into contact with the core 61a of the upper magnet 61. Similarly, a lower pole piece 72 may be arranged to penetrate the bottom wall of the vacuum chamber 10, and magnetically come into contact with the core 62a of the lower magnet 62. The upper and lower pole pieces 71 and 72 and the vacuum chamber 10 may be completely sealed with each other so as to maintain a vacuum state in the vacuum chamber 10.
The pole pieces 71 and 72 may lead magnetic fluxes generated by the upper and lower magnets 61 and 62, respectively, into the vacuum chamber 10. A rubber or ductile metal plate 81 containing ferromagnetic material may be interposed between the upper magnet 61 and the upper pole piece 71 in order for the upper magnet 61 and the upper pole piece 71 to completely come into contact with each other, and a rubber or ductile metal plate 82 containing ferromagnetic material may be interposed between the lower magnet 62 and the lower pole piece 72 in order for the lower magnet 62 and the lower pole piece 72 to completely come into contact with each other.
A ring-type upper protrusion 91 may be formed on a lower surface of the upper pole piece 71, and a ring-type lower protrusion 92 may be formed on an upper surface of the lower pole piece 72. The upper and lower protrusions 91 and 92 may increase the uniformity of a magnetic field formed between the electron-beam emitter 20 and the wafer 30.
However, a conventional electron-beam lithography system, such as the one illustrated in FIG. 1 cannot suitably compensate for a size change of the wafer 30 resulting from a temperature change, because the positions of the upper and lower pole pieces 71 and 72 are fixed. That is, the size of the wafer 30 may change with a temperature change in the vacuum chamber 10 during the patterning of the electron resist 32, whereby the size of the pattern formed on the electron resist 32 may also be changed slightly. Such a size change may cause a problem when a linewidth of several ten nanometers needs to be realized via a semiconductor manufacturing process.